TWI551570B - Cutting tools - Google Patents

Description

Cutting tool

The present invention relates to a cutting tool having a substrate comprising a cermet. In particular, the present invention relates to a cutting tool which has excellent welding resistance and fracture resistance and can exhibit stable cutting performance for a long period of time.

In the past, a sintered alloy (for example, a cermet or a superhard alloy) obtained by bonding a hard particle (hard phase) such as a carbide or a carbonitride with an iron group metal (bonded phase) such as cobalt (Co) or nickel (Ni). ) as a substrate for cutting tools. Usually, the cermet is a hard phase mainly composed of Ti compound particles such as titanium carbide (TiC) or titanium carbonitride (TiCN). On the other hand, the super hard alloy is a hard phase mainly composed of tungsten carbide (WC) particles. A cutting tool having a cermet-containing substrate has the following advantages as compared with a cutting tool having a substrate including a super-hard alloy: (1) excellent wear resistance, and (2) high finishing surface in steel processing Quality, (3) high-speed cutting, (4) lightweight, (5) rich and inexpensive raw materials.

The technique of spraying the surface of the base material of the cutting tool including the sintered alloy to improve the surface properties is described in Patent Documents 1 to 4, for example.

Patent Documents 1 to 3 describe the following cases: by using a drill or not sharpening The substrate of the throwaway tip is sprayed on the surface prior to the coating treatment to remove unnecessary substances on the surface of the substrate, thereby improving the adhesion of the coating layer. Patent Document 4 describes that the surface of the cutting surface of the blade base material containing the cermet is sprayed, and ceramic particles such as alumina particles for polishing the particles are embedded in the surface of the cutting surface. Disperse, thereby improving the resistance to fusion.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2002-536194

Patent Document 2: Japanese Patent Laid-Open Publication No. 2007-007780

Patent Document 3: Japanese Patent Laid-Open No. 09-241826

Patent Document 4: Japanese Patent Laid-Open Publication No. 2010-194669

However, the techniques described in the above Patent Documents 1 to 3 are those in which the surface of the substrate is washed by the blasting treatment to improve the adhesion of the coating, and the surface of the substrate is obtained under the blasting conditions described in the documents. Washing effect, but can't expect the above effect.

On the other hand, in the technique described in the above Patent Document 4, ceramic particles having an average particle diameter of 5 μm to 100 μm are embedded in the surface of the cutting surface of the substrate by the blasting treatment, and are dispersed to perform the surface state. Revamped. However, since the ceramic particles having coarser hard particles than the hard phase constituting the substrate are dispersed, it is easy to cause damage due to breakage of the coarse particles as a starting point.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a cutting tool which has excellent weld resistance and defect resistance and can exhibit stable cutting performance even when used for a long period of time.

The cutting tool of the present invention is provided with a substrate comprising a cermet. Cermet contains hard a phase, a bonded phase, and an unavoidable impurity, the hard phase comprising at least one selected from the group consisting of Ti and at least one selected from Groups 4, 5, and 6 of the periodic table other than Ti, and carbon and nitrogen The compound of the element, the bonding phase is mainly composed of an iron group metal. Further, the surface of the substrate is provided with at least one of alumina particles and zirconia particles having an average particle diameter of 0.5 μm or more and 5 μm or less on the surface of the substrate, and on the surface thereof The concentration of at least one of the aluminum and zirconium is 0.5 atom% or more and 5 atom% or less.

In the cutting tool of the present invention, alumina particles or zirconia particles having a specific average particle diameter (hereinafter sometimes referred to simply as "alumina particles") are dispersed on the surface of the cutting surface of the substrate, and are used as the particles. The concentration of aluminum or zirconium (hereinafter, simply referred to as "aluminum or the like") of the component is within a specific range. By forming a surface state in which such fine alumina particles are dispersed, it is possible to suppress welding on the cutting surface which is contacted by the material to be cut (including the chips) during cutting, and to prevent damage or breakage of the tool. Therefore, it is possible to prevent the cutting performance of the cutting tool from deteriorating, and the use of the cutting tool for a long period of time can also exhibit stable cutting performance.

In the present invention, in addition to the cutting surface, a portion to be contacted by the material to be cut at the time of cutting, for example, a flank surface, or the like, is also dispersed with alumina particles or the like in the same manner as the cutting surface, whereby the welding of the tool can be further suppressed. . However, when alumina particles or the like are scattered on the surface of the cutting edge (cutting edge), there is a problem that the quality of the finished surface of the material to be cut is adversely affected. Therefore, it is preferable to perform a honing treatment or the like. Tip treatment. On the other hand, in the portion which is fixed to the support surface of the holder or the vicinity of the mounting hole and the like, it is not necessary to suppress the welding, so that alumina particles or the like may not be scattered on the surface. That is, it is preferable to disperse alumina particles or the like on the surface of the portion related to the cutting performance other than the blade edge.

When the average particle diameter of alumina particles or the like is less than 0.5 μm, it is difficult to obtain an effect against fusion resistance, and breakage or defect due to welding is likely to occur. On the other hand, in the case of more than 5 μm, the particles become a starting point of breakage, and thus defects are likely to occur during cutting. Moreover, in the case of more than 5 μm, the particles cause damage to the substrate, thereby causing Reduced strength or reduced wear resistance. The above average particle diameter is preferably 1 μm or more and 4 μm or less.

An element such as aluminum is a component derived from the above-described alumina particles or the like.

When the element concentration of aluminum or the like is less than 0.5 atom%, it is difficult to obtain an effect on the weld resistance, and breakage or defect due to welding is likely to occur. On the other hand, when it exceeds 5 atomic%, sufficient fusion resistance can be obtained, but there are many components, and the abrasion resistance tends to be lowered. The concentration of the above element is preferably 1 atom% or more and 2.5 atom% or less.

The average particle diameter of the alumina particles and the like on the surface of the substrate (cutting surface) and the elemental concentration of aluminum or the like are determined as follows. First, the element concentration is a region of 150 μm × 150 μm on the surface of the substrate observed by a scanning electron microscope (SEM), and the region is subjected to energy dispersive X-ray (EDX). The value obtained by quantitative analysis is performed. The average particle diameter is the longest diameter of each particle measured for all the alumina particles detected by EDX in the above region, and the average value thereof is calculated.

Further, it is preferable that the cutting tool of the present invention has an average hardness of from the sintered surface of the substrate surface to a depth of 50 μm or more than 10% of the average hardness from the sintered surface to a depth of 150 μm to 200 μm.

When the hardness of the surface portion of the cermet substrate is higher than the inside, the wear resistance is improved, and on the other hand, the toughness tends to decrease. Therefore, if the sharpness of the material to be cut is welded to the cutting surface, the sharpness is lowered and the cutting resistance is increased, which may cause a defect. In the present invention, it is possible to suppress the occurrence of welding on the cutting surface, and according to the above configuration, the effects of the present invention can be effectively exhibited.

The term "sintered surface" as used herein refers to the surface after sintering.

The cutting tool of the invention can basically be prepared by the raw material powder → mixing. Manufactured by each step of forming, sintering, and blasting.

In the preparation step of the raw material powder, a powder containing Ti and at least one metal selected from Groups 4, 5, and 6 of the periodic table and at least one of carbon and nitrogen, and iron are prepared. A powder of a group metal is used as a raw material powder.

The above compound includes a carbide, a nitride, a carbonitride, and a solid solution of the above metal. Examples of the compound of Ti include TiC, TiN, and TiCN. Further, examples of the metal selected from the group consisting of Groups 4, 5, and 6 of the periodic table other than Ti include, for example, W, Mo, Cr, V, Nb, Ta, Zr, and the like. WC, Mo ₂ C, Cr ₃ C ₂ , VC, NbC, TaC, ZrC, etc. are mentioned. Further, it may be a Ti compound containing Ti and at least one metal selected from the group consisting of metal elements of Groups 4, 5, and 6 of the periodic table other than Ti. For example, a carbonitride (TiWCN) containing Ti and W may be mentioned. These compounds form a hard phase. In the present invention, the Ti compound is a main component of the hard phase (50% or more of the hard phase as a whole, and the Ti compound is the most in the hard phase), and the hard phase is preferably opposite. The total amount of the cermet is 75 mass% or more and 95 mass% or less. Further, the average particle diameter of the powder of the above compound is preferably 0.5 μm or more and 2 μm or less.

Examples of the iron group metal include Co, Ni, and the like. The iron group metal constitutes a bonded phase. In the present invention, the iron group metal is the main component of the bonding phase (in terms of mass ratio, it is 65% or more of the entire bonding phase, and the iron group metal is the most in the bonding phase). Further, the average particle diameter of the powder of the above iron group metal is preferably 0.3 μm or more and 4 μm or less.

For mixing. In the molding step, after the raw material powder is mixed, it is molded into a tool shape to obtain a molded body. The mixing can be carried out by, for example, a ball mill or the like. Forming can be performed by, for example, press forming.

In the sintering step, the formed body is heated and sintered, and then cooled to obtain a cermet-containing substrate. The sintering step includes a temperature increasing step and a cooling step.

In the heating step, for example, in a vacuum of 100 Pa or less, the temperature is raised at a temperature increase rate of 5° C./min or more and 15° C./min or less (primary temperature increase) to 1250° C., and then, at 100°. In a nitrogen atmosphere of Pa or more and 2000 Pa or less, the temperature is raised at a temperature increase rate of 1 ° C/min or more and 5 ° C/min or less (secondary temperature rise) to 1450 ° C or more and 1550 ° C as a sintering holding temperature, and thereafter, This sintering maintains the temperature for a fixed time. The sintering holding time at this time is, for example, 30 minutes or more and 1.5 hours or less. In the secondary temperature rise, the temperature is increased at a low temperature increase rate of 1 ° C / min or more and 5 ° C / min or less, whereby densification of the cermet can be achieved.

In the cooling step, for example, cooling is performed in an Ar or CO gas atmosphere having a pressure of 500 Pa or more and 500 kPa or less. Here, the temperature is raised in a nitrogen atmosphere of a specific pressure by the above-mentioned temperature rising step, particularly the secondary temperature rising. Maintaining, while inhibiting the detachment of nitrogen in the cermet composition. Further, in the cooling step, by setting the conditions for denitrification and decarburization (for example, cooling in an Ar gas atmosphere), the above-mentioned cermet substrate having a higher surface hardness than the inside can be obtained.

In the blasting step, at least one of the alumina abrasive grains and the zirconia abrasive grains (hereinafter, simply referred to as "alumina abrasive grains" or the like) is used to spray the cutting surface of the surface of the cermet substrate. deal with. In addition, by the blasting treatment, alumina abrasive grains or the like are caused to collide with the surface of the substrate (cutting surface), and a part thereof remains on the surface of the substrate, whereby fine alumina particles or the like are scattered on the surface of the substrate to form a fine alumina particle or the like. The surface state in the present invention. The blasting treatment may be either wet or dry, but the wet type is more effective in locally and efficiently spraying the surface of the substrate, which is preferable.

The surface state of the surface of the substrate (cutting surface) can be changed by changing the conditions of the blasting treatment. The conditions of the blast treatment include an average particle diameter of alumina abrasive grains or the like, a concentration of alumina abrasive grains, and the like, an injection pressure, an injection angle, an injection time, and the like. A preferred range of the above conditions is that the alumina abrasive grains and the like have an average particle diameter of 10 μm or more and 50 μm, and the concentration of the alumina abrasive grains or the like is 5% by volume or more and 15% by volume or less, and the injection pressure is 0.5 MPa or more. Further, the spray angle (the angle with respect to the vertical direction of the surface of the substrate (cut surface)) is 15° or more and 60° or less, and the injection time is 5 seconds or more and 20 seconds or less. More preferably, the concentration of the alumina abrasive grains or the like exceeds 5% by volume, the injection pressure is less than 2.5 MPa, and the injection time is 15 seconds or less. Furthermore, the surface states are such that the conditions affect each other, so that even if a certain condition deviates from the above preferred range, the surface state of the present invention is obtained according to other conditions, and thus it is not necessarily limited to the above conditions. The range of good.

Here, the alumina abrasive grains and the like are preferably spherical, and the sphericity is preferably 1.5 or less. A better sphericity is 1.2 or less. The sphericity referred to herein means the ratio of the largest diameter to the smallest diameter of one abrasive grain (maximum diameter/minimum diameter). In the case of spherical abrasive grains, since it is difficult to be broken, when it collides with the surface of the substrate, one of the surfaces of the abrasive grains is partially damaged, and the fragments thereof remain on the surface of the substrate. Therefore, the average particle diameter of the alumina particles or the like on the surface of the substrate (cutting surface) is apt to become small. On the other hand, in the case of the polygonal abrasive grains, there is a case where the surface of the substrate is pierced and left in this state because of the angle. Moreover, since it is easy to be broken, when the particle diameter is large, when the surface of the substrate collides with each other or the abrasive grains collide with each other, there is a case where the sharply broken and sharply pointed pieces pierce the surface of the substrate. Therefore, the average particle diameter of the alumina particles or the like on the surface of the substrate (cutting surface) tends to be large.

In addition, the surface state of the surface of the substrate (cutting surface) by the blasting treatment tends to be such that the lower the concentration of the alumina abrasive grains or the like, the smaller the average particle diameter of the alumina particles or the like remaining on the surface of the substrate, and the like. The lower the element concentration is, the higher the concentration of alumina abrasive grains or the like is, and the larger the average particle diameter of alumina particles or the like remaining on the surface of the substrate, the higher the element concentration of aluminum or the like. In addition, the lower the ejection pressure, the smaller the average particle diameter of alumina particles or the like remaining on the surface of the substrate, and the lower the element concentration of aluminum or the like; the higher the ejection pressure, the oxidation remaining on the surface of the substrate. The larger the average particle diameter of aluminum particles or the like, the higher the element concentration of aluminum or the like. In addition, the smaller the ejection angle, the larger the average particle diameter of alumina particles or the like remaining on the surface of the substrate, and the higher the element concentration of aluminum or the like; the larger the ejection angle, the oxidation remaining on the surface of the substrate. The smaller the average particle diameter of aluminum particles or the like, the lower the element concentration of aluminum or the like. Further, there is a tendency that the shorter the ejection time, the lower the element concentration of aluminum or the like; the more the ejection time Long, the higher the elemental concentration of aluminum and the like.

In particular, by setting the ejection angle to 15° or more and 60° or less, it is easily obtained by wet-jetting from an oblique direction of a vertical direction of the surface of the substrate (cutting surface) of 15° to 60°. The surface state in the present invention. Further, in the case of a substrate of a non-sharpening blade which is substantially perpendicular to the cutting surface and the flank surface, the cutting surface is inclined from the cutting surface side to the flank surface by oblique direction from the vertical direction of the cutting surface toward the cutting edge side. The side is subjected to the blasting process, and not only the cutting surface but also the flank surface can be sprayed. At this time, if the injection angle is 45°, the same blasting process can be performed on the cutting surface and the flank surface.

Here, the portion to be fixed to the bearing surface of the holder or the like which is not related to the cutting does not need to be sprayed, and the sintered surface may be left. Thereby, the reduction in manufacturing cost and the shortening of the manufacturing time can be achieved.

Further, when alumina particles or the like are scattered on the surface of the cutting edge (cutting edge), there is a problem that the quality of the finished surface of the material to be cut is adversely affected, so that the surface of the cutting edge is also sprayed. In time, it is desirable to perform the burr of the tool tip and perform the tool tip treatment.

The cutting tool of the present invention has excellent surface properties such as fine alumina particles dispersed on the surface of the cutting surface, and has excellent weld resistance and defect resistance, and can be stably cut for a long period of time. performance.

[Test Example 1]

The cutting tool of the present invention is fabricated and analyzed and evaluated.

Preparation of TiCN powder having an average particle diameter of 1 μm, WC powder having an average particle diameter of 0.5 μm to 2 μm, TaC powder, NbC powder, ZrC powder, Mo ₂ C powder, Ni powder having an average particle diameter of 1 μm, and Co The powder is used as a raw material powder. These powders were blended in such a manner as to have the composition shown in Table 1, to obtain a raw material powder. Here, the average particle diameter referred to herein means a particle diameter (D50) corresponding to 50% of the cumulative distribution based on the volume of the particles constituting the powder.

After the raw material powder is subjected to wet mixing and pulverization by a ball mill, a spherical granulated powder of 50 μm to 100 μm is obtained by a spray dryer. Next, the granulated powder was press-formed into a blade shape of ISO (International Standardization Organization) standard CNMG120408 at a molding pressure of 98 MPa to obtain a molded body.

The molded body is heated to a temperature of 1,050 ° C at a temperature increase rate of 5 ° C / min to 15 ° C / min in a vacuum of 100 Pa or less, and then N ₂ gas is introduced to 5 ° C / min in a nitrogen atmosphere of 500 Pa. The temperature increase rate was secondarily raised to 1500 ° C (sintering holding temperature), and thereafter, the temperature was maintained and sintering was performed. After maintaining for 1 hour, cooling was carried out under different conditions to obtain two kinds of cermet substrates. Here, the cooling conditions are (A) two conditions of cooling in an Ar gas atmosphere of 200 kPa and (B) cooling in a CO gas atmosphere of 5000 Pa. The cermet substrate when the cooling condition A is used is the cermet substrate A, and the cermet substrate when the cooling condition B is used is the cermet substrate B.

The hardness was measured by micro Vickers for each of the obtained cermet substrates. Specifically, the average hardness and depth of the cross section of the cermet substrate in the thickness direction from the sintered surface of the substrate surface toward the inside to a depth of 50 μm are determined to be 150 μm to 200 μm. The average hardness of the circumference. Here, a straight line is drawn from the arbitrary point on the surface of the substrate, and three positions of Vickers are measured in the range from the surface to the depth of 50 μm and the depth of 150 μm to 200 μm on the same straight line. The hardness (Hv) was measured on each straight line in the depth direction from three points different from the surface of the substrate, and the average value in each range was defined as the average hardness (Hv) of each. As a result, the cermet substrate A has an average hardness of 19 GPa from the surface of the sintered surface to a depth of 50 μm, and an average hardness of 17 GPa from the surface of the sintered surface to a depth of 150 μm to 200 μm, and the hardness of the surface portion is higher than that of the surface. The interior is about 11% higher. Further, the average hardness of the cermet base material B from the sintered surface to a depth of 50 μm and the average hardness from the sintered surface to a depth of 150 μm to 200 μm were both 17 GPa.

Preparing a cermet base material A, 10 B metal ceramic substrate, a ceramic substrate for each metal, average particle diameter of 50 μm, a degree of sphericity of 1.2 or less spherical shape (initial state) of alumina (Al ₂ O ₃ ) The abrasive grains were subjected to a spray treatment under the conditions shown in Table 2. Here, the surface of the cermet substrate was subjected to wet blast treatment from the side of the cutting face to the side of the blade face. In Table 2, the injection angle is set to an angle inclined toward the cutting edge side with respect to the vertical direction of the cutting surface, and is set by adjusting the slope of the injection nozzle.

After the blasting treatment, a 0.04 mm R honing was performed on the tip of each cermet substrate by media honing to perform a tip treatment. Further, a working crusher is formed on the tip of the blade. The cutting tools of Sample Nos. 1 to 11 were obtained in the above manner.

For each of the obtained cutting tools, the average particle diameter of the Al ₂ O ₃ particles on the surface of the cutting surface and the element concentration of Al were measured. Specifically, the elemental concentration of Al was determined by SEM observation of a region of 150 μm × 150 μm on the surface of the cut surface subjected to the blast treatment, and quantitative analysis was performed on the inside of the region by EDX.

Also, the mean particle diameter of Al ₂ O ₃ particles to the region above the EDX detector within all the Al ₂ O ₃ particles, the longest measured by image analysis of each particle diameter, and the average value thereof was calculated to obtain . The results are shown together in Table 2.

For each of the obtained cutting tools, a cutting test was performed under the following conditions to evaluate the cutting performance (weld resistance and defect resistance). The results are shown in Table 3.

(cutting conditions)

Being cut: SCM415 (with 4 U slots)

Cutting speed: 100 m/min

Feed: 0.15 mm/rev

Cut in: 1.0 mm

Cutting state: wet

(evaluation method)

After 30 minutes from the start of cutting, the tip portion was observed, and the presence or absence of welding and breakage was confirmed by an optical microscope. Further, it was measured whether or not the wear amount of the flank surface (Vb) (except for the tool tip treatment amount of 0.04 mm) reached 0.10 mm and the cutting time until the defect occurred. In addition, when the cutting time is less than 30 minutes, it is confirmed whether there is welding or breakage at the end of the cutting.

According to the results of Tables 2 and 3, it is known that Al ₂ O ₃ particles having an average particle diameter of 0.5 μm to 5 μm are dispersed on the surface of the substrate (cutting surface), and the elemental concentration of Al on the surface is 0.5 atom%. In 5 atom% of samples No. 1 to 7, there is no welding, or even if the degree of fusion is small, and there is no damage, and stable cutting can be performed for a long time. Further, according to the comparison between the sample No. 1 including the cermet base material B and the sample No. 2 including the cermet base material A, it was found that the substrate having a hardness of 10% or more higher than the inside was used (ceramic base Material A) can improve wear resistance. The sample No. 2, No. 6, and No of which the average particle diameter of the Al ₂ O ₃ particles on the surface of the cutting surface is 1 μm or more and 4 μm or less, and the elemental concentration of Al is 1 atom% or more and 2.5 atom% or less. .7 Compared with the other samples No. 3 to No. 5, it is excellent not only in welding resistance and defect resistance but also in abrasion resistance.

On the other hand, the cutting time of sample No. 8 to sample No. 11 was short. In sample No. 8 having a high elemental concentration of Al on the surface of the cutting surface, there was no fusion, but the abrasion was performed faster. In sample No. 9 in which the elemental concentration of Al on the surface of the cutting surface was low, fusion occurred and damage or defect occurred. Further, in Sample No. 10 in which the average particle diameter of the Al ₂ O ₃ particles on the surface of the cutting surface was small, welding was caused and damage or defects were caused. In sample No. 11 in which the average particle diameter of the Al ₂ O ₃ particles on the surface of the cutting surface was large, there was no fusion, but damage or defect occurred.

It is to be noted that the above-described embodiments can be appropriately modified without departing from the spirit and scope of the invention, and are not limited to the above configuration. For example, the composition of the cermet or the average particle diameter of the alumina particles can be appropriately changed.

Industrial availability

The cutting tool of the present invention is preferably used in the field of cutting.

Claims (5)

A cutting tool comprising: a base material comprising a cermet; wherein the cermet comprises a hard phase, a bonded phase, and unavoidable impurities, the hard phase comprising Ti and a material other than Ti selected from the group consisting of a compound of at least one metal of Groups 4, 5, and 6 of the periodic table and at least one of carbon and nitrogen, wherein the bonded phase is mainly composed of an iron group metal; and on a cutting surface of the substrate, At least one of alumina particles and zirconia particles having an average particle diameter of 0.5 μm or more and 5 μm or less is dispersed on the surface thereof, and a concentration of at least one of aluminum and zirconium on the surface is 0.5. Atomic % or more and 5 atomic % or less. The cutting tool according to claim 1, wherein the average particle diameter of at least one of the alumina particles and the zirconia particles is 1 μm or more and 4 μm or less. The cutting tool according to claim 1, wherein the concentration of at least one of the above aluminum and zirconium is 1 atom% or more and 2.5 atom% or less. The cutting tool according to claim 2, wherein a concentration of at least one of the above aluminum and zirconium is 1 atom% or more and 2.5 atom% or less. The cutting tool according to any one of claims 1 to 4, wherein the average hardness of the surface of the substrate from the sintered surface to a depth of 50 μm is higher than the average hardness from the sintered surface to a depth of 150 μm to 200 μm. More than 10%.